Many observations show that the simultaneously presented visual events lead to temporally asynchronous percept. A few studies have focused on whether the asynchronous inner experience is related to the difference in neural processing time or to the temporal structure of the stimulus presentation. In the present study, our aim is to get a perceptual handle on the neural processing time for depth and luminance by eliminating a potential confounding factor, namely, temporal structure of stimulus presentation. To accomplish this, we used sinusoidal modulation of depth and luminance, because such modulation has gradual turning points. Our data show that the simultaneous sinusoidal modulation of depth and luminance at same or different locations inevitably results in a perceptually narrow and precise temporal difference, despite the fact that the nature of the turning points in both visual attributes were designed to be the same. Therefore, the temporal difference can be interpreted to stem from neural processing time. Our measurement shows that to get the perceptual synchrony, subjects adjust the relative phase of luminance and depth as if luminance peak is perceived ahead of depth peak.